A million eighteen wheelers moving across the United States. Ten are manned by trained military men who have been trained by Gewrman and Russian professionals to attack electrical, water, gas pipelines bridges and any large groups of opportunities they find befor they are stopped.
Think this is a book you are reading. If they can't stop poor Mexicans they could not stop fifty trained military men. If tons of drugs can come in so can weapons, conventional weapons to do the job. No solitary police force can handle trained military with ten times the fire power.
Your police, judicial and medical groups would not be able to handle this type of problem. That leaves you. You need to be able to cook a meal, deliver a baby, protect your loved ones and set up an island of safety if things go bad. Can you do it?